sONE Way to Inhibit eNOS

The expression of mRNA for endothelial nitric oxide synthase (eNOS), which produces nitric oxide (NO) and thereby plays a critical role in cardiovascular homeostasis, is decreased in endothelial cells overlying atherosclerotic plaques. Although various factors-including cytokines, oxidized low density lipoproteins, and hypoxia-decrease eNOS mRNA stability, the underlying mechanisms are poorly understood. Robb et al. screened a human testes cDNA library with an eNOS cDNA probe and identified an eNOS antisense mRNA (sONE) transcribed from an overlapping transcription unit on the DNA strand opposite to that from which eNOS was transcribed. Using Northern analysis, reverse transcription polymerase chain reaction, and in situ hybridization, the authors showed that sONE mRNA was expressed in various human and mouse tissues but not in human umbilical vein endothelial cells (HUVEC, which do express eNOS). In situ hybridization indicated that sONE and eNOS mRNAs were reciprocally expressed and not colocalized in the same cells. Nuclear run-off analysis, however, indicated that both genes were transcribed in all cell types tested, as did chromatin immunoprecipitation analysis of RNA polymerase II association with the NOS3 and NOS3AS genes (which encode eNOS and sONE, respectively). Human aortic vascular smooth muscle cells transfected with short interfering RNA directed against sONE showed increased eNOS mRNA, whereas HUVEC transfected with sONE showed decreased eNOS. The histone deacetylase inhibitor trichostatin A, which decreases eNOS mRNA in HUVEC, increased sONE mRNA expression before decreasing that of eNOS. Thus, the authors propose that sONE plays a role in the posttranscriptional regulation of eNOS mRNA abundance. G. B. Robb, A. R. Carson, S. C. Tai, J. E. Fish, S. Singh, T. Yamada, S. W. Scherer, K. Nakabayashi, P. A. Marsden, Post-transcriptional regulation of endothelial nitric-oxide synthase by an overlapping antisense mRNA transcript . J. Biol. Chem . 279 , 37982-37996 (2004). [Abstract] [Full Text]